* do endian conversion in usbredirparser where necessary
  * update serialize format (comment only) to be little endian, and also do
    endian conversion there so be -> le and visa versa serialisation becomes
    possible
* check length against max packet size
* check caps for relevant callbacks in parser
* cancel pending packets / active streams before reset?
* add a queue_buf call to parser, use it in host to avoid memcpy of
  "in" bulk transfers